Dr. John Wah

The Science of Soil

When it comes to soil analysis, Dr. John Wah loves getting his hands dirty. Deep in a soil pit near the University of Maryland, John shows us how the color and texture of soil can reveal the age of an archaeological site. He works quickly as the sun begins to set in Maryland, but he doesn't forget to mention how much he loves this job.

SOIL TYPES

Sterile Versus Cultural Soil

Stratigraphy is one of the many ways archaeologists make sense of what they are excavating. By examining the different strata, or layers, of the soil, archaeologists can begin to piece
together a map of the archaeological site over time. Stratigraphy can be used to figure out which soil was associated with human occupation (and therefore likely to contain archaeological materials), but it can also illustrate certain events (like a fire) or natural disasters (like a flood). Stratigraphy is also a useful excavation guide as it can show archaeologists which layers are sterile (not associated with human occupation and not containing anything archaeological) and in which layers they should be keeping an eye out for cultural materials.

Cultural material accumulates where people live and work, leaving artifacts, organic matter (like compost), and other evidence of human activity to build up in the soil. Archaeologists can “see” human occupation layers in the ground, which are often distinct from sterile layers like subsoil, flood sediment, or bedrock. These soil layers provide vital clues about how sites were used, abandoned, and often reused over time.

This material is based upon work supported by the National Science Foundation under Grant Number 1114113. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.